Method of coating base metal withtin



' rolled sheet or strip.

Patented Dec. 28, 1943 PATENT OFFICE METHOD OF COATIgfqBASE METAL WITH William Wallace Murray, Can'onsburg, Pa., as-

signor to Continental Can Company, Inc., New York, N. Y., a corporation of New York No Drawing. Application July 20,1939, Serial No. 2s5.591

' 1 Claim.

ticularly a method of coating black steel or iron with tin.

An object of the invention is to provide a method of electro-plating black steel or iron sheets or strips with tin so as to produce a tin coating layer which is a compacted homogeneouslayer having a continuous mirrorlike surface, which tin layer is strongly adherent to the sheet or strip being coated.

Thevarious processes for electro tin plating black steel or iron strips are fairly efficient, but the deposit of tin on the black sheet or strip is not bright. It is white and lusterless. -Methods have been proposed for brightening the electroplated surface, one of which is to dip the electroplated sheet in hot tallow or palm oil, but such a method is difiicult of operation, as it is necessary to remove the oil that remains on the sheet. If mediums other than oily substances are used,

it is also necessary to remove these mediums in order to obtain a clear, bright surface. Another method of brightening an electro tin platedsheet is to burnish' or polish the plated sheets. This method of brightening is difllcult of operation and expensive, as it removes some of the tin deposited on the sheet, often as much as 25% of the tin- Applicant has developed a new and. improved method of brightening the sheet which does not involve dipping in a hot medium, nor does it result in any appreciable loss of the metal coating being treated. In carrying out the method, the

black plate is cleaned and then electro-plated with tin on the surface or surfaces thereof in any well known way. The electro-deposited tin is crystalline in structure, and asnoted above, has an opaque appearance, often referred to as a satin finish. The coated plate after it comes from the electro-plating machine is passed through a pair of rubber squeeze rolls and then into a drier. The plate is then passed into a cold rolling mill having two rolls rotating at uniform speed. These rolls are of a 'hardnessbetween ninety and one hundred s'celeroscope, and are highly polished. The pressure of the .rolls is adjusted so as to'subject thelcoated sheet or strip to a pressure of between seven hundred and one'thousand pounds per square inch. When the rolls are hardened and polished as noted, this pressure may beused without any marking of the rolls and thus producing the markings on the The mill is a cold rolling mill as noted. However, there is a frictional heat generated due to the pressure at which the rolls are run. The temperature of the rolls during operation is often as high as 245 F. This is, of course, below the melting point of the tin, but it is the temperature I at which tin is malleable.

This rolling operation breaks down the crystals, and the tin being soft and malleable is rolled into a homogeneous layer having a mirrorlike surface. The layer of tin is also. caused by this rolling operation to be pressed into the base plate so that it strongly adheres to the base plate. This" rolling of the sheets or strips produces a bright compacted layer without any appreciable loss of tin. Furthermore, by this rolling of the sheets or strips, a more uniform disingto be used, while still obtaining an eflicient protective coating for the black plate.

The electro tin plating of sheets 'may be accomplished by passing the sheets automatically flrst'througlr a cleaner, then the electro-plating machine, then the squeeze rolls and drier, and finally through the cold rolling mill, and these units may be so timed and adjusted that the sheets will pass in continuous succession. In place of the sheets, strips of steel or iron may be passed through the several units in the order stated, and the strip electro-plated, cold rolled,

and thus a very compact bright coating of tin produced on the strip. I

While the invention is particularly adapted to the coating of base metal with tin, it may also be used'to great advantage for the brightening of electro-plated copper, zinc or cadmium sheets without departing from the sp rit of the invention as set forth in the appended claim.

Having thus described the invention, what I 40 claim as new and desire to secure by'Letters Patent' is: I

The method of coating black iron with tin consisting in electrodepositing a layer of tin on the black iron, squeezing and drying said layer and subjecting the-deposited layer to cold rolling with rolls from ninety to one hundred sceleroscope hardness and highly polished, said rolls rotating at uniform speed and under pressure from seven hundred to one thousand pounds per square inch, whereby the heat incident to rolling renders the tin malleable. permitting said electrodeposited layer to be compacted into a homogeneous layer strongly adhering to the black iron WILLIAM WALLACE MURRAY. 

